Among current stereoscopic image displaying systems, there is one skill which utilizes a liquid crystal display panel to alternatively display a left-eye image and a right-eye image by a time-divisional approach. A user can experience stereoscopic perception when the user puts on a pair of shutter glasses, at such time the user's left eye receives the left-eye image and the user's right eye receives the right-eye image. A stereo image displaying system like the above-described needs to increase a frame rate up to 120 Hz, also has to increase vertical blanking interval (VBI) in order to provide sufficient time for the human eyes to receive the images.
FIG. 1 is a schematic diagram showing scanning timing and backlight turn-on timing in a conventional liquid crystal display panel. FIG. 2 is a schematic diagram showing data writing timing and backlight turn-on timing in the conventional liquid crystal display panel. In FIG. 1 and FIG. 2, the horizontal axis is a time axis, and the vertical axis shows corresponding positions of the liquid crystal display panel from top to bottom. The liquid crystal display panel is scanned from top to bottom through the gate lines. One image frame displaying period includes a displaying interval and a vertical blanking interval.
The conventional stereoscopic image displaying system works as follows. When writing the right-eye image data, two pieces of eyeglasses of the shutter glasses are turned off and the backlight is turned off as well. When every right-eye image data has been written, a right-piece eyeglass of the shutter glasses is turned on, scanning procedures turn into VBI, and the backlight is turned on as well. At this time, the right-eye image enters into the user's right eye. Similarly, when writing the left-eye image data, two pieces of eyeglasses of the shutter glasses are turned off and the backlight is turned off as well. When every left-eye image data has been written, a left-piece eyeglass of the shutter glasses is turned on, scanning procedures turn into VBI, and the backlight is turned on as well. At this time, the left-eye image enters into the user's left eye. By repeating above operations, the left-eye image and the right-eye image are experienced as a stereoscopic image in human's brain.
The left-piece eyeglass and the right-piece eyeglass of the shutter glasses are made of liquid crystal materials. The liquid crystal molecules need a response time for reaching a maximum transmittance. In the conventional stereoscopic image display system, the shutter glasses and the backlight are turned on at the same time and have the same turn-on duration. In this conventional skill, the image experienced by the user is incomplete and the image quality is not as good as anticipated. Moreover, the liquid crystal molecules in the liquid crystal display panel need a response time so as to present proper images. The duration which is from writing the image data into the liquid crystal display panel to turning on the shutter glasses is descending from top to bottom. That is to say, the liquid crystal molecules being located at the upper region of screen have much more response time. The response time for the liquid crystal molecules being located at the lower region of screen is relatively insufficient. As shown in FIG. 3, in a case of utilizing a single-domain over driving look-up table in conventional skills, the voltages for driving the liquid crystal molecules at the respective regions of screen are the same. The liquid crystal molecules being located at the upper region of screen are over driven while the driving intensity for the molecules being located at the lower region of screen is insufficient. Therefore, the brightness appeared on the upper region and the lower region is different, and this lead to poor image quality.
Referring to FIG. 4, another conventional stereoscopic image displaying system adopts a multi-domain over driving look-up table, which can select a best LUT (look-up table) value by determining positions on the screen. For example, the voltage used for driving the liquid crystal molecules at the upper region of screen is V1, the voltage used for driving the liquid crystal molecules at the middle region of screen is V2, and the voltage used for driving the liquid crystal molecules at the lower region of screen is V3, wherein V1<V2<V3. The duration which is from writing the image data into the upper region of the liquid crystal display panel then to turning on the shutter glasses is much longer; hence, a smaller LUT value (e.g., V1) is selected to modify the response velocity of the liquid crystal molecules thereon. The duration from writing the image data into the lower region of the liquid crystal display panel to turning on the shutter glasses is much shorter, and therefore a larger LUT value (e.g., V3) is selected to accelerate the response velocity of the liquid crystal molecules thereon. In such a manner, the response of the liquid crystal molecules at the upper, middle, and lower regions of the liquid crystal display panel is almost finished simultaneously at the time of turning on the shutter glasses.
However, in the conventional skill utilizing the multi-domain over driving LUT, the image presented on the lower region of screen still has poor quality since the response speed of the liquid crystal molecules is inherently limited and the liquid crystal molecules can not response instantly. Image crosstalk is easily to be appeared on the lower region of screen, and thereby causing a so-called ghost image. In addition, it needs to consistently determine the LUT value according to positions on the screen when utilizing the multi-domain over driving look-up table. This will make the system over-loaded.